serial versus parallel data transfer

[E=MC2]

serial and parallel data transfer

parallel data transfer refers to the type of data transfer in which a group of bits are transferred simultaneously while serial data transfer refers to the type of data transfer in which a group of data bits are transferred one bit at a time. so that means that the amount of data transferred serially is less that the data transferred parallelly per second.

but serial data transfer requires less cables so if the data has to be transmitted over longer distances serial data transfer is preffered.

uptil this point all is well and good. the point that i dont understand is that in computers many of the interfaces that were once parallel are now being made serial. serial ATA, hyperTransport and Multiol are all serial interfaces. and all these interfaces have data transfer rates greater than the previous parallel interfaces. how is that so???? how come serial data transfer is faster than parallel data transfer?

 

[Andre3000]

serial vs parallel data transfer

You are right...
The parallel ports are faster, and esier because they dont requiere multiplexing. Tthe thing is that since the serial ports reqier less pins, or lines, the HW can be smaller. So engeniers have dedicated more efort on serial ports and protocols, so they can make smaller devices, imagine a palm with a parallel port conector instead of a USB conector, the conector alone would be to big. So its not that they are faster, they are just more developed becase of the efort put into them.

 

[eternal_nan]

serial parallel data transfer

Parallel buses are hard to run at high frequencies for
a number of reasons the greatest of which are:
1. It is hard to route many signals across a board without introducing timing variation between them - the more variation the lower maximum frequency is.
2. Many wires switching simultaneously produce lots of EMI and interfere with each other. More EMI -> less maximum frequency.

Although serial interfaces have less bits, due to the above two reasons they can be clocked at MUCH higher rates than parallel interfaces and the clock speed increase outweighs the bandwidth decrease due to less bits being transferred parallely.

PCI -> 33MHz
AGP8X -> 266MHz
HyperTransport -> 1GHz DDR (2 giga-transfers), 16 2-16 serial lanes
PCI Express -> 2.5GHz 1-16 lanes serial
HyperTransport and PCIE are slated to scale up to >6GHz. The numbers speak for themselves.

 

[trogger]

difference between serial and parallel transfer

Following up from what eternal_nan said - it's called "data skew". This is when minute timing differences in parallel cables cause data to arrive out of sync - so you can't speed it up indefinitely. Thus, people choose serial, which requires less wires and doesn't suffer from any data skew.

 

[puviarasu]

parallel data transfer

In serial data transfer you can impliment many data error corrrection algorithms so by suppose if the data is correpted while passing through the cable, it can be recovered easily and serial data can be easily interfaced to optical fibers (future communication link). and in PCB also it is easy to rout and isolate 2 to 4 wires(serial data) than 8 to 64 wires (parallel data).

Regards
Puvi

 

[platonas]

serial vs parallel bus

Always parallel is faster, this is why CPU, cache and RAM communicate in parallel and this is why a 64bit CPU is faster than a 32 or 8 bit one.
On the contrast, a hard disk reads serially. The Hard disk has 2 or more heads. Each head must read the data and then pass it through a special circuit to combine it to parallel. Now new ideas said, do not do this, just transmit it serially. It will need less time to manipulate data serially than to make it parallel compatible. In theory it is also cheaper since less electronics are involved, in practice it should be more expensive since it is a new and faster technology that should sell.
Peripherals outsite the PC are prefered to be of serial communication for many reasons but the speed. The main problem is interference/interaction between datalines. This is a different story I think.

 

[bluewave]

parallel and serial data transfer

Serial communication could be less Xtalk, less skew, and more differential pairs.

 

[mipedja]

difference between serial & parallel transfer

Parallel- short distance.
Serial - longer distance.

 

[puviarasu]

why is serial communication faster than parallel

Recently PCI Express(serial) is introduced and another standard PCI X(high speed parallel), but you would have heard about PCI Express only because it is compact use the same type of connector with huge bandwidth the main thing is that it is serial, now the serial bus standards are overtaking parallel ones because of their high speed flexibility as you can easily change the internal protocol not useful or possible in parallel transfer, and design and production cost.

 

[zlop]

serial vs parallel data

Member puviarasu is right. But additionly there is another thing he(she?) doesn't notice: Nowadays, clock fre is a most important thing to determine the performance of a sys. Due to the EMI reasons and the cross noise between wires, the SERIAL is better than the PAR.

 

[JoseLeonardo]

serial and parallel data transfer.

I think that tha serial communication is use in interconection of devices in computer systems, this is true, because of serial communication is more easy for detection of mistakes in the communication, and the computer systems of today are work faster and mistake are currently, for this reason, this systems are require detection of mistake.

 

[truebs]

difference between serial and parallel bus

We cannot decide that Whether a data transmission through serial or parallel is faster ,unless and untill we have the details of data rate supported.
Although general notion is right that parallel transmission is faster than serial but ..conditions apply.
Say i am transmitting 8 bits parallely at data rate 1bps. So i transmit only 8 bitsps ,however if i have a system that can transmit 10bps serially ,this is faster inspite of being serial transmission.

Now the question might arise that i may use 8 lines of the same serial system , but then the problem lies in distance supported and system design.

 

[savadi]

twisted pair serial or parallel

you must compare serial links with parallel with same technology. as technology adveces and engineers like to design serial links, the speed also increses.

 

[cherrytart]

serial vs. parallel bus

It's always going to cost more to build 8 copies of a line driver than 1, This need not be a prohibitive consideration when your interconnects are printed circuits and the connectors are solder joints. But then for an interface you also need 8 copies of the input and output connectors and the wires. At some point it will be cost effective to accept a byte throughput one eighth of what the technology supports to reduce cabling and connector costs.

 

[Big Boy]

serial versus parallel bus

On a drawing board, parallel look faster than serial. At least, this is what we were told since our basic electronic courses.

However, there is more than drawing paper, i.e. actual physics involved.

At higher frequencies, you gat a whole lot of new constraints. For example, you no longer can use 0V/5V signals. This is why higher frequency bus go to 3.3V and even lower.

A little theory here... However, going lower voltage meen that the bus is more sensible to noise. Moreover, the longer the data lines go, the higher the noise level. A way to counter-interact this is to use what's called 'differential lines'. A differential line is simply a pair of lines which are tightly coupled (run side by side for example). Then, the driver always put a logical 0 or 1 on one line, and the inverse on the other line. For example, it would put 0.5V on one line while putting 0V on the other line (to represent a logical 1), or 0V on one line and 0.5V on the other line (to represent a logical 0). The theory is that if noise occur, which will result in voltage spike on the lines, since both lines run side by side, that voltage spike will occur simultaneously on both lines. At the receiving end, even if the lines are noisy, the *difference* of voltage across the two lines of the pair will be the same, and reflect the transmitted data. So, the receiving end just look for this voltage difference, and extract a logical 0 or 1 depending on which line have higher voltage. The good thing is that you don't require a common refferene between the transmitter and receiver (like a ground). So, even if the transmitting device and receiving device have different GND (due to noise for example...), this doesn't affect the transmission. Differential voltage pair are used in many applications, like Ethernet (twisted pair cables).

So, due to the above reason, serial links can go much higher frequency that parallel links. And at 2GHz+ frequencies, even a 2 inch trace on a PCB benefit from the above concept.

 

[nutty boy]

parallel and serial data transfers

I think that the most common mehod for communication with the computer is via USB and i think it's aerial communication but is enhasment

 

[puviarasu]

serial vs. parallel data transfer

Nowadays the normal bus is vanishing because of the increase in speed of the processor and nowadays processors uses differential pairs for interconnection as it is noise immune and efficient they are used for both parallel (link ports in Tiger SHARC) and serial data busses (PCI Express) nowadays people go for serial ports as the design process takes less time and it always point to point link and all the burdens go in to programming side. if you consider the parallel data transfer it will be always a shared bus so the bus speed is shared among all the peripherals so the total bandwidth per peripheral will be less compared to the serial PTP bus.